1. Field of the Disclosure
Embodiments disclosed herein relate to purified brine, such as brine having reduced organic content, for example a reduced content of epoxy resin, epihalohydrin, reaction products, catalysts and/or solvents. Embodiments disclosed herein also relate to processes and apparatus for obtaining brine having reduced organic content. Other embodiments disclosed herein relate to improvement of processes and apparatus wherein brine is used in the processes or apparatus so as to include brine therein having reduced organic content and/or relates to brine obtained therefrom. Embodiments disclosed herein are useful in various processes and technologies, such as processes involving water, waste water, and brine purification, such as in chlorine/alkali processes and processes involving production of epoxy resins. Thus, embodiments disclosed herein also relate to processes and apparatus for purification of brine generated by industrial processes, such as the production of epoxy resins. Purified brine may be used in industrial processes such as the chlor-alkali process for the electrolytic conversion of brine to chlorine gas and sodium hydroxide or hypochlorite.
2. Background
In chemical processes, there is a need to obtain a maximum utility of incoming process streams, as well as the ability to recycle process streams, or to use byproducts from one process in other processes, particularly in nearby processes. Such uses of process streams are environmentally and economically desirable.
In the production of epoxy resins by the reaction of polyhydric phenols with epihalohydrins and alkali metal hydroxides, an alkali metal halide salt is produced as a byproduct. The salt can be either in aqueous solution, if the production process involves the contact of multiple liquid phases, or as a solid salt if azeotropic water removal is used during the reaction step.
The byproduct salt or brine is typically contaminated with organic compounds, such as the product epoxy resin, the epihalohydrin, reaction products from the hydrolysis of the epihalohydrin, the phase transfer catalyst or cosolvent from the reactor, or another solvent. It is desirable to purify the byproduct salt or brine before disposal or reuse.
JP04060994(B) and JP60081176(A) are directed to separation of an inorganic salt formed as a byproduct, by adding a concentrated aqueous solution of the inorganic salt formed as a byproduct to an epoxy resin reaction product, separating the resultant mixture into three layers of a resin solution layer, an aqueous layer of the inorganic salt and a slurry layer of the inorganic salt, and filtering off the inorganic salt from the slurry layer. As indicated in the English abstract of these Japanese documents, a compound having a hydroxyl or amino group is reacted with an epichlorohydrin and an aqueous solution of an alkali while removing water by the azeotropic distillation to produce an epoxy resin. In the process, in order to remove an inorganic salt formed as a byproduct, a concentrated aqueous solution of the above-mentioned inorganic salt is added to the above-mentioned reaction product directly or after distilling away the excess epichlorohydrin and diluting with an organic solvent, and the resultant mixture is agitated, allowed to stand and separated into three layers of a resin solution layer, an aqueous layer of the inorganic salt and a slurry layer of the inorganic salt. The inorganic salt is then filtered off from the slurry layer of the inorganic salt, and the inorganic salt, which is a byproduct, is efficiently separated from the above-mentioned reaction product as crystals in high purity.
U.S. Pat. No. 4,751,280 discloses a method of producing epoxy resin by reaction with azeotropic water removal followed by drying, filtering and washing steps. As disclosed therein, salt removal can be accomplished by “any suitable mechanical means” such as filtration or centrifugation, and a vertical basket centrifuge is cited as a particularly suitable device.
EP0356854 B1 discloses a method of treating organic-contaminated salts by washing with a solvent, deliquoring the salt cake, and drying the salt to give a salt containing small amounts of residual organic contamination. The example describes washing a contaminated salt from epoxy resin production in a basket centrifuge with epichlorohydrin and an epichlorohydrin/1-methoxy-2-propanol mixture, followed by deliquoring in the basket centrifuge. The salt was then dried in a rotary dryer.
DD216471 A1 discloses mixing the reaction products from epoxy resin manufacture (epoxy resin, inorganic salts and solid organic byproducts) with an organic solvent for >15 minutes, followed by addition of water, followed by decanting of the aqueous phase to give improved phase separation.
DD155780 A3 discloses the use of centrifugation to separate an epoxy resin/solvent layer from an aqueous salt layer.
CS190218 B1 discloses the separation, which includes separation by gravity or centrifuge, of epoxy resins from reaction mixtures into a salt layer and a resinous layer containing epichlorohydrin and epoxy resin.
CS176770 B1, CS174508 B1 and CS136171 disclose the use of a centrifuge for separation of the organic and aqueous phases in an example of the preparation of an epoxy resin.
SU245368 discloses the use of filtration to remove salt formed in the preparation of epoxy novolak resins.
SU191118 describes the continuous removal of a saturated aqueous salt layer from a resin solution during epoxy resin production, followed by azeotropic distillation of the water and subsequent removal of the salt by filtration.
CN1850635 A discloses a method of treating waste brine from an epoxy resin process by neutralization, filtration, film distillation, crystallization, and solid-liquid separation. Also disclosed is the use of biological treatment for wastewater with low salt content.
CN1884079 A discloses a method of purifying contaminated solid salts from epoxy resin production by reacting with HCl, neutralizing, removing floating impurities, and multiple crystallization and solid/liquid separation steps.
CN1792832 A discloses a method of extracting waste brine from an epoxy resin process with a solvent, neutralizing with an acid to pH 5-9, adding a coagulant and/or a flocculant, filtering, concentrating by evaporation, then crystallizing the salt from the wastewater to obtain a solid salt product.
CN1124231 B and CN1263051 A disclose a method of treating wastewater from an epoxy resin process by decanting the organic phase, concentrating, and crystallizing to obtain a solid salt. A portion of the mother liquor from the crystallization step is discharged, and a portion may be recycled. The condensate from the evaporative crystallization may be used for wash water.
GB2320020 A discloses a method for removing halogenated organic compounds from wastewater using powdered lignite or activated carbon. The method is described as applicable to wastewater from a variety of chemical production processes, including epoxy resin production.
JP3409915 B2 discloses the use of centrifugal separation tanks with rotational disks to improve the phase separation of epoxy resins from wastewaters.
JP03094884 A discloses the use of activated carbon to adsorb impurities including polymer from epoxy resin wastewater. COD is said to be reduced from 10,000 mg/L to 1200 mg/L using a batch treatment.
PL151776 B2 discloses a method of treating epoxy resin wastewater by use of multiple evaporative crystallization/filtration steps. pH adjustment and salt washing are also done. An organic phase containing glycerol and polyglycerols is recovered.
U.S. Pat. No. 4,976,864 A and EP362934 B1 disclose a method for treating epoxy resin wastewater by hydrolysis under alkaline conditions followed by removal of 90% of NaCl by evaporative crystallization or electrodialysis. The use of a combination of anaerobic and aerobic digestion is also described.
DD243503 A1 discloses the use of heating and decanting to remove insoluble epoxy resin from a wastewater containing NaCl and solids.